This invention relates to a catheter for infusing therapeutic or diagnostic agents into the tissue of organs, and more particularly to a catheter having a mechanism for controlled extension of an injection needle.
Targeted delivery of therapeutic or diagnostic agents, such as occurs in gene therapy, is very desirable but often presents a difficult challenge. A potential benefit of targeted delivery is that there is an increased efficiency obtained by the precise placement of the therapeutic agent. There are several problems to his procedure which must be overcome in order to obtain satisfactory results from such therapy, such as the problems of obtaining access to the delivery site, transporting the therapeutic agent to the desired site, injecting the therapeutic agent at the proper depth within the organ tissue, steering the distal end of the catheter to a desired location within the organ prior to infusing the agent, and positioning the distal tip of the catheter at precisely the same location where prior measurements have indicated that the drug should be infused. It is also important to for a physician to be able to monitor the position of the infusion needle with respect to the wall of the organ. In the case of an organ, such as the heart, in which the walls are in constant motion, the activity of positioning and monitoring the position of the distal tip of the catheter, or infusion needle, becomes especially difficult.
U.S. Pat. No. 3,598,119 discloses a medical device for injecting drugs in which the injection needle is guided through an inner lumen of a catheter for insertion of the needle under skin tissue. A bladder at the distal end of the catheter may be inflated through another lumen for holding the point of the needle point in a fixed position beneath the skin.
U.S. Pat. No. 4,578,061 discloses a catheter for injecting a liquid into a vein, or artery, through an injection needle which is longitudinally movable beyond the distal end of the catheter. A dual chamber system is utilized within the catheter tip to provide for movement of a plunger to extend the injection needle and also to allow for a plunger to be used to apply a predetermined dose of medication through the injection needle.
U.S. Pat. No. 4,578,061 discloses an injection catheter having a longitudinal movable needle which may be moved through a lumen in order to extend out of the side wall of the catheter for injecting a liquid into a blood vessel. The needle is normally retracted into the device so that the needle will not penetrate tissue as the device is moved through a body duct. Thereafter, the needle is moved out of the side of the catheter into a vessel wall in order to infuse a liquid into the wall of a vessel.
U.S. Pat. No. 5,244,460 is directed toward a method for improving blood flow to the heart. More particularly this patent is directed toward a medical procedure for improving the growth of cardiac blood vessels by inserting a catheter into a coronary artery and injecting into the heart a blood vessel growth promoting peptide through an injection port of the catheter.
U.S. Pat. No. 5,419,777 is directed toward a catheter for injection of a fluid into body cavities such as coronary vessels and arteries. This patent, as is the case with the ""061 patent, illustrates the use of an injection needle which protrudes laterally through the side walls of the distal tip of the catheter. In the case of drug injections to be made into coronary vessels and arteries, it is very desirable to have the needles extend out of the side walls of the catheter and at an acute angle to the walls of the vessel in order to penetrate the walls of the vessel for injection of the agent.
U.S. Pat. No. 5,431,168, assigned to the same assignee as the present patent application, is directed toward a steerable catheter which includes a puller wire for controlling the distal end of the catheter from a control handle which is mounted on the proximal end of the catheter.
Copending U.S. patent application Ser. No. 09/019,453, entitled xe2x80x9cIntracardiac Drug Delivery,xe2x80x9d assigned to an affiliated company of the assignee of this application, discloses an injection catheter system for infusing a diagnostic or therapeutic agent into the wall of an organ which includes an electromagnetic sensor disposed within the distal tip of the catheter for providing very precise location information for the distal tip of the catheter. The subject matter of this copending patent application is incorporated by reference into the subject patent application.
Copending U.S. Pat. No. 6,165,168 discloses an injection catheter where extension of the injection needle is determined by the amount of movement that is allowed in the injection handle. The injection handle is adjustable, permitting the physician to adjust the needle extension to the desired length. Although this design has several advantages, it can cause the needle to buckle inside the catheter due to frictional force between the needle and the housing in which the needle is mounted, which can result in unpredictable needle extension.
The present invention is directed to a catheter for infusing therapeutic or diagnostic agents into the tissue of organs having a system for predicable extension of the infusion needle, thereby reducing the variability that can occur when the extent of the needle extension is controlled by the needle control handle.
In one embodiment, the invention is directed to a catheter comprising a catheter body comprising a flexible tubing having proximal and distal ends and at least one lumen therethrough. The catheter further includes a tip section comprising a flexible tubing having proximal and distal ends, with the proximal end of the tip section mounted at the distal end of the catheter body. The tip section has a needle passage extending therethough. The needle passage has a proximal region having a proximal diameter and a distal region having a distal diameter less than the proximal diameter. A needle control handle is provided at the proximal end of the catheter body. An injection needle extends through the tip section, catheter body, and needle control handle and has a proximal end attached to the needle control handle and a distal end within the needle passage. The injection needle is longitudinally slidable so that its distal end can extend beyond the distal end of the tip section upon suitable manipulation of the needle control handle. A needle stop is mounted on a portion of the injection needle that is positioned within the proximal region of the needle passage. The needle stop has a distal end that is sized to prevent passage of the portion of the injection needle on which the needle stop is mounted from passing into the distal region of the needle passage. The needle stop limits the distance that the injection needle can be extended beyond the distal end of the tip section.
In another embodiment, the invention is directed to a catheter comprising a catheter body comprising a flexible tubing having proximal and distal ends and at least one needle passage extending therethrough. The needle passage has a proximal region having a proximal diameter and a distal region having a distal diameter less than the proximal diameter. An injection needle extends through the catheter body and has a distal end within the needle passage. The injection needle is longitudinally slidable so that its distal end can extend beyond the distal end of the catheter. A needle stop is mounted on a portion of the injection needle that is positioned within the proximal region of the needle passage. The needle stop has a distal end that is sized to prevent passage of the portion of the injection needle on which the needle stop is mounted from passing into the distal region of the needle passage. The needle stop limits the distance that the injection needle can be extended beyond the distal end of the catheter body.